#define _CRT_SECURE_NO_WARNINGS
#include<vector>
#include<iostream>
using namespace std;
int massage(vector<int>& nums) {
    int n = nums.size();
    if (n == 0)return 0;
    if (n == 1)return nums[0];
    vector<int> dp(n);
    dp[0] = nums[0], dp[1] = max(dp[0], nums[1]);
    for (int i = 2; i < n; i++) {
        dp[i] = max(dp[i - 2] + nums[i], dp[i - 1]);
    }
    return dp[n - 1];
}
int main() {
    vector<int> v = { 1,2,3,1 };
    int ret=massage(v);
    cout << ret << endl;
    return 0;
}